The present invention relates to an improved interface for a constant velocity joint, grease cover and flange assembly to reduce shearing forces caused by applied torque.
There are generally four (4) main types of automotive drive line systems. More specifically, there exists a full-time front wheel drive system, a full-time rear wheel drive system, a part-time four wheel drive system, and an all-wheel drive system. Most commonly, the systems are distinguished by the delivery of power to different combinations of drive wheels, i.e., front drive wheels, rear drive wheels or some combination thereof. In addition to delivering power to a particular combination of drive wheels, most drive systems permit the respectively driven wheels to rotate at different speeds. For example, the outside wheels must rotate faster than the inside drive wheels, and the front drive wheels must normally rotate faster than the rear wheels.
Drive line systems also include one or more Cardan (Universal) and Constant Velocity joints (CVJ""s). Cardan joints are the most basic and common joint type used, for example, on propshafts. Although highly durable, Cardan joints are typically not suited for applications with high angles (e.g. greater than 2 degrees) because of their inability to accommodate constant velocity rotary motion. Constant Velocity joints, in contrast, are well known in the art and are employed where transmission of a constant velocity rotary motion is desired or required. For example, a tripod joint is characterized by a bell-shaped outer race (housing) disposed around an inner spider joint which travels in channels formed in the outer race. The spider-shaped cross section of the inner joint is descriptive of the three equispaced arms extending therefrom which travel in the tracks of the outer joint. Part spherical rollers are featured on each arm.
One type of constant velocity universal joint is the plunging tripod type, characterized by the performance of end motion in the joint. Plunging tripod joints are currently the most widely used inboard (transmission side) joint in front wheel drive vehicles, and particularly in the propeller shafts found in rear wheel drive, all-wheel drive and 4-wheel drive vehicles. A common feature of tripod universal joints is their plunging or end motion character. Plunging tripod universal joints allow the interconnection shafts to change length during operation without the use of splines which provoke significant reaction forces thereby resulting in a source of vibration and noise.
The plunging tripod joint accommodates end wise movement within the joint itself with a minimum of frictional resistance, since the part-spherical rollers are themselves supported on the arms by needle roller bearings. In a standard ball roller type constant velocity joint the intermediate member of the joint (like the ball cage in a rzeppa constant velocity joint) is constrained to always lie in a plane which bisects the angle between the driving and driven shafts. Since the tripod type joint does not have such an intermediate member, the medium plane always lies perpendicular to the axis of the drive shaft.
Another common type of constant velocity universal joint is the plunging VL or xe2x80x9ccross groovexe2x80x9d type, which consists of an outer and inner race drivably connected through balls located in circumferentially spaced straight or helical grooves alternately inclined relative to a rotational axis. The balls are positioned in a constant velocity plane by an intersecting groove relationship and maintained in this plane by a cage located between the two races. The joint permits axial movement since the cage is not positionably engaged to either race. As those skilled in the art will recognize, the principal advantage of this type of joint is its ability to transmit constant velocity and simultaneously accommodate axial motion. Plunging VL constant velocity universal joints are currently used for high speed applications such as, for example, the propeller shafts found in rear wheel drive, all-wheel drive and 4-wheel drive vehicles.
The high speed fixed joint (HSFJ) is another type of constant velocity joint well known in the art and used where transmission of high speed is required. High speed fixed joints allow articulation to an angle (no plunge) but can accommodate much higher angles than with a Cardan joint or other non-CV joints such as, for example, rubber couplings. There are generally three types of high speed fixed joints: (1) disk style that bolts to flanges; (2) monoblock style that is affixed to the tube as a center joint in multi-piece propshafts; and (3) plug-on monoblock that interfaces directly to the axle or T-case replacing the flange and bolts.
A HSFJ generally comprises: (1) an outer joint member of generally hollow configuration, having a rotational axis and in its interior, a plurality of arcuate tracks circumferentially spaced about the axis extending in meridian planes relative to the axis, and forming lands between the tracks and integral with the outer joint part wherein the lands have radially inwardly directed surfaces; (2) an inner joint member disposed within the outer joint member and having a rotational axis, the inner joint member having on its exterior a plurality of tracks whose centerline lie in meridian planes with respect to the rotational axis of the inner joint member in which face the tracks of the outer joint member and opposed pairs, wherein lands are defined between the tracks on the inner joint member and have radially outwardly directed surfaces; (3) a plurality of balls disposed one in each pair of facing tracks in the outer and inner joint members for torque transmission between the members; and (4) a cage of annular configuration disposed between the joint members and having openings in which respective balls are received and contained so that their centers lie in a common plane, wherein the cage has external and internal surfaces each of which cooperate with the land surfaces of the outer joint member and inner joint member, respectively to locate the cage and the inner joint member axially.
In joints of this kind, the configuration of the tracks in the inner and outer joint members, and/or the internal and external surfaces of the cage are such that, when the joint is articulated, the common plane containing the centers of the balls substantially bisects the angle between the rotational axis of the joint members. As indicated above, there are several types of high speed fixed joints differing from one another with respect to the arrangement and configuration of the tracks in the joint members and/or to the internal and external surfaces of the cage whereby the common bisector plane is guided as described above thereby giving the joint constant-velocity-ratio operating characteristics. In each design, however, the cage is located axially in the joint by cooperation between the external cage surface and the surfaces of the lands facing the cages surface.
The outer surface of the cage and cooperating land surfaces of the outer joint member are generally spherical. When torque is transmitted by the joint, the forces acting in the joint cause the cage to be urged (by e.g. ball expulsion forces) towards one end of the joint which end will depend on the respective directions of the offsets of the tracks in the inner and outer joint members from the common plane when the joint is in its unarticulated position. To reduce the normal forces acting on the cage as a result of these ball expulsion forces, the amount of spherical wrap by the outer joint member lands is maximized for increased cage support.
In a disc-style constant velocity fixed joint, the outer joint member is open on both ends and the cage is assembled from the end opposite the end towards which the cage is urged by the ball expulsion forces under articulated load conditions. Assembly of the cage into the outer joint member is typically accomplished by either incorporating cage assembly notches into one of or a pair of lands in the outer joint member, or by sufficiently increasing the bore diameter of the outer joint part to allow the ball cage to be introduced into the outer joint part.
In a mono-block constant velocity fixed joint, also called a xe2x80x9cmono-block high speed fixed jointxe2x80x9d, the outer joint part is a bell-shaped member having a closed end. Accordingly, the cage must be assembled from the open end of the outer joint member. To accommodate assembly of the cage into the outer joint part, the bore diameter of the outer joint part must be sufficiently increased to allow assembly and/or assembly notches must be incorporated into at least one opposing pair of the outer joint member lands to allow introduction of the cage. typical driveline system incorporates one or more of the above joints to connect a pair of propeller shafts (front and rear) to a power take off unit and a rear driveline module, respectively. These propeller shafts (xe2x80x9cpropshaftsxe2x80x9d) function to transfer torque to the rear axle in rear wheel and all wheel drive vehicles.
Most constant velocity universal joints are sealed in order to retain grease inside the joint while keeping contaminants and foreign matter, such as dirt, water, and the like out of the joint. In order to achieve this protection, the constant velocity joint is usually enclosed at the open end of the outer race by a sealing boot made of rubber, thermoplastic or urethane. The opposite end of the outer race is sometimes formed by an enclosed xe2x80x9cdomexe2x80x9d known in the art as the greasecap. In addition to retaining grease and protecting the joint from contaminants, the sealing boot functions to remain durable throughout millions of propeller shaft articulation revolutions while operating continuously within predetermined temperature ranges (typically xe2x88x9240C to 120C) at speeds up to 6000 revolutions per minute. Specifically, a constant velocity joint is affixed to a grease cover which, in turn, is affixed to a mating flange of a propeller shaft. The constant velocity joint, grease cover and flange assembly is typically held together by a plurality of bolts.
It has been found, however, that over time when torque is applied to the propeller shaft, resulting shearing forces may cause the connecting bolts to loosen and, in extreme cases, to become partly disengaged.
Consequently, a need exists for a constant velocity joint, grease cover and mating flange assembly having an improved interface to reduce if not eliminate the above shearing forces and resultant effects on the connecting bolts.
It is a principal object of the present invention to provide a constant velocity joint, grease cap and mating flange assembly having an improved interface.
In carrying out the above object, there is provided an improved constant velocity joint, grease cover and flange assembly. The constant velocity joint has a mating surface with a first anti-slip portion. Similarly, the flange has a mating surface with a second anti-slip portion. Still further, the grease cover has a first mating surface with a third anti-slip portion adapted to receive and mate with the first anti-slip portion of the constant velocity joint, and a second mating surface with a fourth anti-slip portion adapted to receive and mate with the second anti-slip portion of the flange. According to the invention, the respective anti-slip portions function to reduce shearing forces on connecting bolts of the assembly caused by applied torque.
To achieve the above described reduced shearing forces, there is further disclosed a method of providing an improved constant velocity joint, grease cap and flange interface. The method comprises providing a constant velocity joint having a first mating surface with a first anti-slip portion. The method further comprises providing a flange having a mating surface and a second anti-slip portion. Finally, the method comprises providing a grease cover having a first mating surface with a third anti-slip portion adapted to receive and mate with the first anti-slip portion of the constant velocity joint, and a second mating surface having a fourth anti-slip portion adapted to receive and mate with the second anti-slip portion of the flange.
In a preferred embodiment of both the assembly and method described herein, the third and fourth anti-slip portions comprise a plurality of circumferentially distributed dimples extending radially from opposing surfaces of the grease cover. Still further, in this preferred embodiment, the first and second anti-slip portions of the constant velocity joint and flange respectively comprise a plurality of circumferentially distributed recesses adapted to receive and mate with the dimples of the grease cap. In alternative embodiments, dimples may be replaced with recesses and vice versa. Still further, dimples and recesses may be combined on the same surfaces provided that corresponding changes are made to the mating portion. i.e. dimples mate with recesses.